The proposed project addresses the need for a rigorous trial to test the efficacy of a behavioral intervention to control Early Childhood Caries (ECC) among affected low-income Hispanic children. ECC remains a highly prevalent and consequential chronic disease (44% of U.S. children affected by age 5 years) and minority, immigrant, and low-income populations experience disproportionately high occurrence, severity, and lack of treatment. Largely preventable, ECC results in avoidable pain and infection for children, stress and lost work productivity for caregivers, and costly surgical repair by dentists. Standard practice treats ECC primarily through surgical dental repair, an approach that addresses neither the natural history of the disease nor the family-level behavioral determinants that mediate its occurrence (i.e., dietary habits and home fluoride use). As professional consensus emerges regarding the value of behavioral disease management for ECC, these approaches remain largely unstudied, notably so among high-risk Hispanic children. MySmileBuddy, developed and piloted through our prior NIH research grant, has been shown to be acceptable to our target audience of immigrant Hispanic families and feasible to implement by Community Health Workers. MySmileBuddy uses innovative health technology to assess a child's ECC risk, inform parents about the caries process, develop tailored oral health goals, and create a family- centered action plan bolstered by social support. The proposed project will prepare for a behavioral randomized controlled trial (B-RCT) of MySmileBuddy by developing: organizational and management structures; detailed descriptions of roles and responsibilities of study personnel; partnerships with key organizations to assure feasibility; and logistics for study implementation, including cohort recruitment and retention, sample size determination, measurements, data collection and analysis procedures. The proposed project will develop a U01 proposal for a B-RCT by developing: a Clinical Protocol, Manual of Procedures, and Detailed Timeline that spell out plans for collecting, managing, securing, and analyzing data; assessing MySmileBuddy's cost-effectiveness; and reporting and disseminating findings. The study design and training plans will maximize intervention implementation and protocol fidelity and ensure the reliability and validity of measurements. The significance of this R34 planning work is that it will assure a B- RCT that is methodologically sound and ready to implement. The theoretical significance of the B-RCT is improved understanding of the behavioral determinants of ECC progression, while the practical and policy- relevant significance is substantiating a low-cost behavioral complement to contemporary surgical care that can reduce or eliminate ongoing disease.